Twisting of textile filaments



May 17, 1960 D. F. ARTHUR ETAL v 2,936,570

TwIsTING oF TEXTILE FILAMENTS Filed Nov. 16, 195e .2/ .2:5 2529 5 39 /57Q/ g i I,27 Gaf @57 INVENTORS ATTORNEYS United States Patent 4O TWISTINGF TEXTILE FILAIVIENTS David Foxall Arthur, West Pontnewydd, Cwmbran, andAlan Frederick Weller, Newport, England, assignors to British NylonSpinners Limited, Pontypool, England Application November 16, 1956,Serial No. 622,546 4 Claims. (Cl. 57-157) The present invention relatesto improvements to, and modifications in, the processes of twisting andcrimping textile filaments as described and claimed in the specificationof our copending U.S.A. patent application No. 595,543.

In the above patent specification there is described, inter alia, -aprocess for imparting a false twist to a running textile filamentwherein the filament is caused to bear against, and be rotated by, theinner peripheral surface of one end portion at least, of a rotatingtwist-tube and on one side of the axis thereof. The internal surface ofthe tube at least at its yarn-contacting end-portion is composed of anon-abrasive material having a high coeiiicient of friction with thefilament. Such a falsetwisting process can, if the filament is heat-setwhile in the highly twisted state, be very conveniently used to insert acrimp in thermoplastic filaments such as nylon as is described in theaforementioned specification.

It is stated in the specification that, once the twist-tube is rotatingat or above a given minimum angular velocity, the value of turns perinch of twist inserted in multifilament yarns is very little affected byvariations input tension or speed of the yarn, o-r by variations inspeed ofthe tube above the critical speed. This minimum angular velocitycan be calculated for any given value of turns per inch of twist anddenier of textile filament.

We have now discovered that, although the above proposition is broadlytrue, there is a relationship between filament speed, the speed of thatportion of the inner peripheral surface `of the tube with which thefilament makes contact and filament input and output tensionson the onehand and turns per inch of twist inserted 0n the other, for any givendimensions of the tube and of the angles of entry land exit made with itby the filament. According to this relationship, there is an optimumvalue for the ratio of 'filament speed to the peripheral speed ofthatpart of the tube with which the filament makes contact; that is tosay, that at a certain value of this ratio, the greatest number of turnsper inch of twist will be inserted in the filament. This is, of course,due to the complicated frictional effects between the filament and theinner peripheral surface of the tube resulting from` the forward motionof the filament and the relative transverse motion of the tube surface.

if the abovementioned ratio is of a value lower than the optimum, itwill be necessary, in order to achieve the desired turns per inch oftwist, to have an input tension higher than is desirable for effectivesetting of the filament in the highly twisted state. For the bestheatsetting results, it is desirable to allow the filament to shrinksomewhat during heat-setting, say by at least 2% and preferably by atleast 3% and such a shrinkage can normally only occur in nylon filamentsfor example, if the tension in the lament is low, i.e. of the order of0.2. gram per denier, or less, under the normal conditions fo-rheat-setting such a filament on the run. The conditions (i.e.temperature and time of heating and soV 2,936,570 Patented May 17, 1960race cooling) for the effective heat-setting of a running textilefilament will depend on the nature and denier of the filament, thenature of the heating and cooling media and the speed of the filament,as well as on the amount of contraction allowed during the settingtreatment as a whole.

If the above-mentioned speed ratio is of a value significantiy higherthan the optimum, for example 0.9 or greater, not only will the turnsper inch of twist not be as great as could be achieved, but also, owingto the increased tension multiplying factor, the output tension (withthe drawing-olf speed remaining constant) will be of a value such as maycause undue wear on the filamentcontacting surface of the twist-tube.

The discovery concerning the optimum value of the abovementioned ratioenables a satisfactory compromise to be worked out between theconflicting requirements of the twist factor necessary for producing thenecessary crimping deformations and of the conditions required to setthose deformations effectively.

The value of the ratio for optimum conditions when crimpingmultifilament yarn of nylon according to the invention is around 0.8.However, since the value of the output tension rises sensiblyproportionally to the value of the speed ratio (the drawing-off speed ofthe filaments remaining constant) it is only desirable to `work at theoptimum ratio for the lower denier yarns (say, up to denier) as the4value of the output tension becomes too high for satisfactory crimpingwhen working at the optimum speed ratio and an input tension of 0.2 gramper denier with heavier denier yarns. In the latter case, a ratio tof0.54 produces the best results in all the circumstances. It can be said,therefor, that for textile filaments as defined in our previousspecification No. 595,543 with which the invention is solely concerned,the value of the speed ratio must be at least 0.50, and is preferably ofa value of 0.8 for nylon multifllament yarns lof up to 70 denier, whenthe input tension is of the order of 0.2 grams per denier, or suchtension as wiil allow of a sensible amount, say 3%, of shrinkage of thefilament during setting, without impairing the stability of running ofthe filaments. Multilament Vyarns or cords of up to 840 denier can besuccessfully false-twisted according to the invention, although crimpedyarns lare normally required to be of a much lower denier than this. i

The present invention, therefore, comprises a process for imparting afalse twist to a running textile filament wherein the filament is causedto bear against, and be rotatedby, the inner peripheral surface of oneend portion, at least, of a rotating twist-tube and on one side of theaxis thereof, the internal surface of the tube at that one end portionat least being composed of a non-abrasive material having a highcoefficient of friction with the `filament and wherein the ratio of thefilament speed to the surface speed of that part of the innerlperipheral surface of the tube with which the filament makes contact isnot less than 0.5. The invention also comprises a process for crimping athermoplastic textile filament wherein a false twist is imparted to thesaid filament according to the above-mentioned process and the filamentis heated over succeeding lengths of itself which are in the highlytwisted condition to an extent sufficient to set the twist thereinwhilst the filament is allowed to contract by a sensible amount, thesucceeding lengths of twist-set filament are then cooled beforeuntwisting, and the filament is untwisted and then wound up under lowtension.

An understanding of the invention may be faciiitated by reference to theaccompanying drawings forming a part of this specification in which:

Figure l is a schematic showing of the crimping of thermoplasticmultifilament yarn according to the invention; and

Figure 2 is an enlargedl sectional view of the twist tube, rotatedclockwise so that its axis is horizontal, schematically shown in Figurel.

Referring to Figure 1, yarn 13 of thermoplastic material is withdrawnover one end of a supply package 17, and is then passed around the drumof a magnetic hysteresis tensioner 19 which imposes a constant outputtension on the yarn. The yarn is then led through an infra-red heatingdevice 21 comprising a glass tube 23 having electric resistance coilswound therearound.

After passing through the tube, the yarn travels through the air for asucient time for it to cool below its plastic state, and then passesinto one end of av twist-tube 27 such as that illustrated in Figure 2.The twist-tube is mounted with its axis at an angle to the vertical suchthat the yarn led directly through and from the heating device makescontact with one side 29 of the inner peripheral surface of a rubberbush (see Fig. 2) Contained within the twist-tube. The yarn is led fromthe twisttube around a pulley-wheel 31, which ensures contact of theyarn with the bush at this end thereof, and therefore along the wholelength lof the bush. After passing over kthe pulley-wheel 31 the yarn isled through the nip of a pair of forwarding rolls 33, 35, which feed theyarn forward at a slightly greater speed than that at which it iseventually wound up by the roll 37v on the'package 39. Thus the yarnbetween the rolls 33, 35 `and the wind-up package 39 is relaxedslightly. In operation, the yarn is given a high degree of false twistby means of the twist-tube, which high twist in `one direction feedsback through the heating device to the tensioning device, and is set;the yarn in its twist-set conditionl is allowed to cool somewhat betweenthe heating device and the twist-tube; twist in the opposite sense isimparted to the twistset yarn directly on leaving the twist-tube; andthe now crimped yarn is wound up under a low tension.

Referring now to Figure 2, the twist-tube comprises a ixed annularportion i, and a drive annular portion 3 mounted on roller bearings 5, 7therein. The driven annular portion 3 is rotated by band 9. FittedWithin the driven annular portion 3 is a rubber bush 11, the innersurface of which makes direct contact with the yarn 13. The yarn is ledto and away from the tube at an angle to the asis thereof. Thus the yarnwhen suitably tensioned is kept in contact with the'whole length of' theinner surface of the rubber bush, and also with the two curved endportions thereof.

In order to demonstrate more clearly the interaction of the variousfactors referred to above, the following examples show the values of thefactors for the best operating conditions when crimping multilamentnylon yarns of various deniers.

, Y4 rubber with carbon' black filler, and having the followingdimensions: Y Y

(i) Length of bush 1% (ii) Internal diameter of cylindrical portion ofbush- 5A; (iii) Thickness of bush 7/16 (iv) Radius of curvature of endlips o-f bush 7A@ A 30 denier ten-lament nylon yarn was led from asupply packageV to an additive tension device which ap-V piied a tensionofy 6 grams (0.2 gram per denier) as input tension on the yarn reachingthe twist-tube which was rotating at 2,000 r.p.m. Between the tensiondevice and the twist-tube the yarn was led through an infra-red heaterin order to heat-set the yarn in its'highly-twisted state, there being agap of somel 6 inchesv between the end of the heater and the twist-tubeto all-ow the hot yarn to cool suiliciently to below the temperature atwhich it is in a plastic condition. The infra-red heater was of the typein which the heatingV element (an electric resistance) is positionedalong one focus of an elliptical reflecting tubeV and the yarn passesalong the other focus of the tube. The temperature of a therrnocouple inequilibrium in the yarn path Ywithin the tube was 242 C. The yarn wasdrawn through the twist tube at 265 feet a minute by a roller positionedon the other side of the twist-tube from the heating tube, the yarnbeing wrapped twice around the roller, and the yarn was caused to enterone end of the twist-tube along a path the projection of which was at anangle of S5 to the proiection of the axis of the tube (an angle ot' atleast SOY being preferred according to the invention), to run in lirm,steady contact with the inner peripheral surface of the rubber bush onone side of the axis thereof without any tendency to jump, and to leavethe twist-tube along a path at a similarly-defined angle of y". Thetension in the yarn between the twist-tube and the drawing-off rolls wasmeasured at 22 grams. Between the drawing-oft' rolls and the wind-up theyarn was relaxed, so that thel winding was carried out under lowtension. speeds ratio (yarn speed to surface speed of inner periphery ofbush) was 0.81, the twist inserted in the yarn was 131 turns per inch,and the yarn was allowed to contract by 3.5% between the drawing-offrolls and the tension device. v

Examples 2 to 5 Forconvenience', theseV examples are presented in tableform. The* apparatus was similar to that described in Example 1,v andthese examples show the varied andV 5'0" varying. conditions' inprocesses similar to that of Example 1 for increasing deniers of nylonyarn crimped at 26'5 feet a minute. It' will be observed that thetemperature of thev setting tube is increased with denier and that theconditions are always'such that at least 3% contraction of 55 the yarnisl allowed.

Heat Yarn Angular setting Twist Denier] speed,l Speeds velocity EntryExit ten- Percent temper turns Example Number Number of Iect/ ratio oftube, tension, sion, shrinkatnres per laments :ninr'.p.m. grams gramsage in yarn inch ute path,

2 45/15 2 65 0. 81 2, 000 8 30 3. 3 250 105 3.... (iO/2,0 265 0.81 2,O00 12 42 3. 4 255 101 e 100/34 265 0.54 3, 000 20 42 4. 2 270 72 5150/50 265 t). 4 3, 000 30 66 4. 0 290 57 Example I The twist-tube usedin this example, andv in all thel following examples, was one such as isdescribed and illustrated herein and in the specification and drawingsof our cto-pendingk application No. 595,543 having. an in ternal surfaceinthe form of a bush, composed of natural 'I5U ments for crimpingvcomprising the steps of tensioning" Although a yarn speed of 265feet/minute is lexcmpii-YV Inches Under these optimum conditions, whenthe y a running length of textile filament between iixed points,twisting the filament length by frictional contact with an encircling,annular rotating surface composed of nonabrasive material having a highcoeicient of friction with the textile filament, the diameter of saidsurface exceeding the diameter of said lament, whereby a plurality ofturns of false twist is imparted to the lament for each revolution ofsaid surface, the speed of said filament being at least half theperipheral speed of said surface, the axis of said surface beingangulated with respect to the filament path approaching and leaving saidsurface, applying heat to said filament length at a point leading saidsurface sufficiently to permit substantial cooling therebetween, andmaintaining the tension in the portion of said length leading saidsurface at a value not exceeding about 0.2 gram per denier, whereby thelament is permitted to shrink at least about 2.0% between the point ofheat application and said surface.

2. A process as delined in claim 1, wherein the angle between the axisof said surface and the filament path approaching said surface is atleast 80.

3. A process as defined in claim ,1, wherein the speed of said filamentis about 0.8 times the peripheral speed of said surface, andthe filamentdoes not exceed denier. I

4. A process as deiined in claim 1, wherein the false twisted filamentis wound up under low tension.

References Cited in the file of this patent UNITED STATES PATENTS2,463,620 Heberlein Mar. 8, 1949 2,673,442 Long Mar. 30, 1954 2,753,679Von Scholler et al. July 10, 1956 2,803,109 Stoddard et al. Aug. 20,1957 FOREIGN PATENTS 440,546 Italy oct. 13, 194s 496,585 Great Britain]Dec. 2, 1938 500,823 Great Britain Feb. 16, 1939

